Because of their high speed and flexibility, electrophotographic or laser beam printers are becoming increasingly popular. While this technology has reached a high state of perfection in connection with black and white printing, where it is desired to form multicolored prints many problems remain. A typical example of the state of the art multicolor printers is described in the Hitachi U.S. Pat. No. 4,467,334. To produce the multicolored images, the surface of the photosensitive drum is scanned with a plurality of laser beams sequentially with the toner being applied immediately after the latent image for a particular color is formed on the drum surface.
The foregoing apparatus and method has two major drawbacks. Firstly, the surface to which the first toner color has been applied subsequently passes by the developers wherein the second and third color toners are contained. Because the toner applied to the drum is held by relatively weak electrostatic forces, some of the toner leaves the surface of the drum and contaminates the subsequent developers, thereby altering the desired color balance. The second drawback of the device shown in the Hitachi patent is that the paper upon which the image is printed can be no wider than the photosensitive drum since the drum rolls along the surface of the paper sheet in the same direction of the sheet. Obviously, this limits the application of such printers to comparatively small reproductions, unless extremely costly and very large drums are employed.